Surface controlled, subsurface safety valves are commonly used to shut in oil and gas wells in the event of a failure or hazardous condition at the well surface. Such safety valves are typically fitted into the production tubing and operate to block the flow of formation fluid upwardly therethrough. The subsurface safety valve provides shutoff of production flow in response to a variety of out-of-range safety conditions that can be sensed or indicated at the surface. For example, the out-of-range safety conditions may include a fire on the platform, a high or low flow line temperature or pressure condition, or operator override.
During production, a hydraulically operated subsurface safety valve is typically held open by the application of hydraulic fluid pressure conducted to the subsurface safety valve through an auxiliary control conduit, which extends along the tubing string within an annulus between the tubing and the well casing. Flapper type subsurface safety valves utilize a closure plate which is actuated by longitudinal movement of a hydraulically actuated piston, which can be a rod-style piston, a concentric tubular piston, or an electro-mechanical operator. The flapper valve closure plate is maintained in the valve open position by an operator tube which is extended by the application of hydraulic pressure onto the piston. A pump at the surface pressurizes a reservoir which delivers regulated hydraulic control pressure through the control conduit. Hydraulic fluid is pumped into a variable volume pressure chamber and acts against the crown of the piston. When, for example, the production fluid pressure rises above or falls below a preset level, the control pressure is relieved such that the piston and operator tube are retracted to the valve closed position by a return spring. The flapper plate is then rotated to the valve closed position by a torsion spring or tension member.
Often, the flapper valve has a valve seat that includes a downwardly facing, conical segment having a sloping sealing surface and the flapper closure plate has a complementary, sloping annular sealing surface which is adapted for surface-to-surface engagement against the conical valve seat surface. Typically, the flapper closure plate is supported for rotational movement by a hinge assembly which includes a hinge pin and a torsion spring or tension member. It will be appreciated that structural distortion of the flapper valve closure plate, or damage to the hinge assembly which supports the flapper closure plate, can cause misalignment of the respective sealing surfaces, thereby producing a leakage path through the safety valve.
Such misalignment will prevent correct seating and sealing of the flapper closure plate, and a large amount of formation fluid may escape through the damaged valve, which may cause waste and pollution. During situations involving damage to the wellhead, the well flow must be shut off completely before repairs can be made and production resumed. Even a small leak through the flapper safety valve in a gas well can cause catastrophic damage.
Generally, the flapper closure plate is machined from forged billet stock using multi-axis milling processes, which ensure consistent material properties. However, machining via traditional removal techniques of the downhole equipment may limit the geometries and design of the downhole equipment. For example, the flapper closure plate is generally a solid metal piece having a geometry that, while increasing performance of the flapper valve, inhibits complex machining to include additional features. As valve size increases, flapper size and weight also increase, which imparts higher loads and stresses on the torsion closing spring, often requiring alternate closing spring structures and methods or damage to the valve. Increased flapper weight may result in slower valve closure, which may decrease safety valve performance.
The present disclosure is directed to printed subsurface equipment, such as a printed flapper plate, and methods that overcome one or more of the shortcomings in the prior art.